Methods of polishing an object using slurry compositions

ABSTRACT

In a slurry composition for chemical mechanical polishing, a method of preparing the slurry composition and a method of polishing an object using the slurry composition, the slurry composition includes a cerium oxide abrasive particle having a rare earth element other than cerium as a dopant, and an aqueous medium for dispersing the cerium oxide abrasive particle. The cerium oxide abrasive particle doped with the rare earth element may have an enhanced fracture strength as being compared with a pure cerium oxide abrasive particle, and also may reduce an amount of large or agglomerated particles and generation of a scratch on a polished surface of an object.

RELATED APPLICATION DATA

This application claims the benefit of Korean Patent Application No.10-2008-0064217, filed on Jul. 3, 2008, in the Korean IntellectualProperty Office, the disclosure of which is incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

Embodiments of the present invention relate to slurry compositions,methods of preparing the slurry compositions and methods of polishing anobject using the slurry compositions. More particularly, embodiments ofthe present invention relate to slurry compositions for chemicalmechanical polishing that may be employed in manufacturing asemiconductor device.

BACKGROUND

Chemical mechanical polishing (CMP) is a technique that may be used insemiconductor fabrication for planarizing a semiconductor wafer. The CMPtechnique may include chemical etching of a slurry composition and amechanical abrasion caused by an abrasive and a polishing pad. The CMPtechnique was developed by IBM in the late 1980s, and so far it has beenwidely used in global planarization for manufacturing a semiconductorchip.

In a CMP process, a surface of a substrate may be mechanically polishedby rubbing the surface of the substrate with an abrasive and protrusionsof a polishing pad, and further chemically polished by a chemicalreaction with components contained in a slurry composition. The abrasivecontained in the slurry composition may mechanically grind the substrateunder a pressure provided from a polishing apparatus. Silica or siliconoxide (SiO₂), ceria or cerium oxide (CeO₂), alumina or aluminum oxide(Al₂O₃) and the like may be generally used as an abrasive.

Some commercial abrasives employ undoped or pure cerium oxide particles.A pure cerium oxide abrasive may include a crystal grain having afaceted shape and a wide distribution of the diameter of the particles.Such pure cerium oxide abrasives may frequently cause a scratch defecton a wafer, which may generate a decrease in the production yield and/orreliability deterioration of a semiconductor device.

SUMMARY

Embodiments of the present invention provide slurry compositions for CMPhaving improved polishing characteristics. Exemplary embodiments alsoprovide methods of preparing the slurry compositions. Exemplaryembodiments further provide methods of polishing an object using theslurry compositions.

According to some exemplary embodiments, a slurry composition for CMPincludes a cerium oxide abrasive particle having a rare earth elementother than cerium oxide as a dopant, and an aqueous medium fordispersing the cerium oxide abrasive particle.

In an exemplary embodiment, the rare earth element may include samarium(Sm).

In other exemplary embodiments, an amount of the rare earth element maybe in a range of about 10 to about 40% by mole, based on a total mole ofcerium and the rare earth element. In further exemplary embodiments, theamount of the rare earth element may be in a range of about 20 to about30% by mole.

In some exemplary embodiments, the cerium oxide abrasive particle mayhave a mean grain diameter of less than about 29 nm. The cerium oxideabrasive particle may have a mean diameter of a secondary particle in arange of about 70 nm to about 120 nm.

In some exemplary embodiments, the aqueous medium may include adispersing agent and water. An amount of the dispersing agent may be ina range of about 0.05 to about 5% by weight, based on a total weight ofthe slurry composition.

In some exemplary embodiments, an amount of the cerium oxide abrasiveparticle may be in a range of about 1 to about 10% by weight, based on atotal weight of the slurry composition.

According to other exemplary embodiments, there is provided a method ofpreparing a slurry composition for CMP. In the method, a cerium salt anda salt of a rare earth element other than cerium may be co-precipitatedin an aqueous solution to obtain a precipitate including a rare earthelement and cerium. The precipitate may be thermally treated to form apreliminary cerium oxide abrasive particle doped with the rare earthelement. The preliminary cerium abrasive particle doped with the rareearth element may be grinded to form a cerium oxide abrasive particledoped with the rare earth element. The slurry composition may beobtained by dispersing the cerium oxide abrasive particle doped with therare earth element in an aqueous medium.

In an exemplary embodiment, the precipitate may be thermally treated ata temperature of about 600° C. to about 900° C.

According to still other exemplary embodiments, there is provided amethod of chemically and mechanically polishing an object. In themethod, a slurry composition may be provided between an object and apolishing pad. The slurry composition may include a cerium oxideabrasive particle having a rare earth element other than cerium as adopant, and an aqueous medium for dispersing the cerium oxide abrasiveparticle. A surface of the object may be polished by contacting theobject with the polishing pad.

In an exemplary embodiment, the object may include a substrate having atrench and an insulation layer for device isolation on the substrate tofill the trench.

In other exemplary embodiments, the object may include a substrate onwhich a conductive structure is formed and an insulating interlayer onthe substrate to cover the conductive structure.

According to further exemplary embodiments, the slurry compositionincludes a cerium abrasive particle doped with a rare earth element. Thecerium oxide abrasive particle doped with a rare earth element may havea proper shape and/or size for reducing generation of a scratch defecton a surface of an object as compared with a pure cerium oxide abrasiveparticle. The cerium abrasive particle doped with a rare earth elementmay have an improved fracture strength, so generation of debris or fineparticles may be reduced during a grinding process and the amount of alarge or agglomerated particle dispersed in the slurry composition mayalso be reduced. The slurry composition may reduce generation of adefect (e.g., a scratch) on an object by employing such an abrasiveparticle having a controlled shape and size of a crystal grain and anarrow distribution of a particle diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings. FIGS. 1-13 represent non-limiting, exemplary embodiments asdescribed herein.

FIG. 1 is an electron microscopic picture showing a crystal grain of acerium oxide abrasive particle doped with a rare earth element.

FIG. 2 is an electron microscopic picture showing a crystal grain of apure or undoped cerium oxide abrasive particle.

FIG. 3 is a flow chart illustrating a method of preparing a slurrycomposition according to exemplary embodiments.

FIG. 4 is a flow chart illustrating a method of polishing an objectaccording to exemplary embodiments.

FIG. 5 is a schematic diagram illustrating a CMP apparatus that may beemployed in polishing an object according to exemplary embodiments.

FIGS. 6A to 6D are cross-sectional views illustrating a method ofmanufacturing a semiconductor device according to some exemplaryembodiments.

FIGS. 7A to 7C are cross-sectional views illustrating a method ofmanufacturing a semiconductor device according to other exemplaryembodiments.

FIG. 8 is a graph showing size distributions of abrasive particlescontained in the slurry compositions obtained in Example 1 andComparative Example 1.

FIGS. 9 and 10 are electron microscopic pictures showing abrasiveparticles included in the slurry compositions obtained in Example 1 andComparative Example 1, respectively.

FIGS. 11 and 12 are wafer maps illustrating a distribution of scratchdefects on a wafer polished using each of the slurry compositionsobtained in Example 1 and Comparative Example 1.

FIG. 13 is a graph showing the number of scratches generated on a waferaccording to the doping amount of the rare earth element.

DETAILED DESCRIPTION

Various exemplary embodiments will be described more fully hereinafterwith reference to the accompanying drawings, in which some exemplaryembodiments are shown. Exemplary embodiments may, however, be embodiedin many different forms and should not be construed as limited to theexemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. In the drawings, the sizes and relative sizesof layers and regions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itmay be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numerals refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of example embodiments.

Spatially relative terms, e.g., “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would be oriented “above” the other elements orfeatures. Thus, the exemplary term “below” may encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Exemplary embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized exemplary embodiments (and intermediate structures). As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments should not be construed as limitedto the particular shapes of regions illustrated herein but are toinclude deviations in shapes that result, for example, frommanufacturing. For example, an implanted region illustrated as arectangle may, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofthe present invention.

Unless otherwise defined, all terms including technical and scientificterms used herein have the same meaning as commonly understood by one ofordinary skill in the art to which example embodiments belongs. It willbe further understood that terms, e.g., those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Embodiments of the present invention provide slurry compositions. Thesecompositions are particularly useful for CMP. According to exemplaryembodiments, a slurry composition may include a ceria (i.e., ceriumoxide) abrasive particle doped with a rare earth element, and an aqueousmedium for dispersing the cerium oxide abrasive particle. The ceriumoxide abrasive particle doped with a rare earth element may have anarrow size distribution and a proper shape of a crystal grain forreducing generation of a scratch defect on a surface of an object, ascompared with a pure cerium oxide abrasive particle. Thus, the slurrycomposition may reduce generation of a defect (e.g., a scratch) on anobject by employing such an abrasive particle.

In exemplary embodiments, the cerium oxide abrasive particle may bedoped with a rare earth element excluding cerium. Examples of the rareearth element may include samarium (Sm), scandium (Sc), yttrium (Y),lanthanum (La), praseodymium (Pr), neodymium (Nd), promethium (Pm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium(Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and thelike with the proviso that the rare earth element is not cerium. Theserare earth elements may be used alone or in a combination thereof. Insome exemplary embodiments, the cerium oxide abrasive particle mayinclude samarium (Sm) as a dopant.

The amount of the rare earth element contained in the cerium oxideabrasive particle may be changed to control the shape and/or size of acrystal grain, the polishing rate, and the amount of large oragglomerated particles dispersed in an aqueous medium, etc. In someexemplary embodiments, the amount of the rare earth element may exceedabout 5% by mole, based on a total mole of cerium and the rare earthelement. In other exemplary embodiments, the amount of the rare earthelement may be greater than or equal to about 10% by mole. In stillother exemplary embodiments, the amount of the rare earth element may bein a range of about 10˜40% by mole, or in a range of about 20˜30% bymole.

In exemplary embodiments, the cerium oxide abrasive particle doped withthe rare earth element may primarily have a sphere-like crystal grain(i.e., a primary particle).

FIG. 1 is an electron microscopic picture showing a crystal grain of acerium oxide abrasive particle doped with a rare earth element, and FIG.2 is an electron microscopic picture showing a crystal grain of a pureor undoped cerium oxide abrasive particle.

As shown in FIGS. 1 and 2, the pure or undoped cerium oxide abrasiveparticle may have a faceted crystal grain as having a clear [111]crystal face, because pure cerium oxide may have a tendency to grow intoa cube. However, the cerium oxide abrasive particle doped with a rareearth element may have a sphere-like crystal grain, because crystalfaces and [100] may grow uniformly in cerium oxide doped with a rareearth element.

During crystal growth of cerium oxide, the rare earth element may act toencapsulate a crystal growing face and may further inhibit the growth ofa specific crystal face. The sphere-like crystal grain may reducegeneration of scratches on a surface of an object to be polished, ascompared with a faceted crystal grain. While a cerium abrasive particleis prepared by grinding, the sphere-like crystal grain may also suppressformation of fine or ultra-fine particles smaller than a particle havingan average diameter.

In exemplary embodiments, the cerium abrasive particle doped with a rareearth element may have a mean diameter of a crystal grain smaller thanthat of a pure cerium oxide abrasive particle even though these ceriumoxide abrasive particles are formed under substantially the sameconditions. The rare earth element may inhibit growing of a cerium oxidecrystal on a growing surface, so the size of a crystal grain may becomesmaller. In some exemplary embodiments, the cerium abrasive particledoped with the rare earth element may include a crystal grain having amean diameter smaller than about 29 nm. In other exemplary embodiments,the mean diameter of a crystal grain may be in a range of about 25 nm toabout 27 nm. The size of the crystal grain of the cerium oxide abrasiveparticle may be determined using an electron microscope, or using anX-ray diffraction analysis and the Scherrer's equation as shown below asEquation 1.

d=0.9λ/(β cos θ)  [Equation 1]

In Equation 1, “d” denotes a diameter of a crystal grain, “λ” denotes awavelength of X-ray, “β” denotes a full width at half maximum in a peak,and “θ” denotes a diffraction angle of the peak.

In exemplary embodiments, the cerium oxide abrasive particle doped withthe rare earth element may be a secondary particle including at leastone crystal grain (i.e., a primary particle). The mean diameter of thesecondary particle may be changed to improve dispersibility, thepolishing rate, the number of scratches, etc. For example, the meandiameter of the secondary particle may be in a range of about 50 nm toabout 200 nm. In other embodiments, the mean diameter of the secondaryparticle may be in a range of about 70 nm to about 120 nm.

In further exemplary embodiments, the cerium oxide abrasive particledoped with the rare earth element may reduce the amount of large oragglomerated particles dispersed in the slurry composition, as comparedwith using pure cerium oxide abrasive particles. For example, the rareearth element (e.g., Sm) may enhance a fracture strength of a ceriumoxide abrasive particle. When the fracture strength increases,generation of fine or ultra-fine particles or debris may be suppressedduring a grinding process, and the size distribution of particles maybecome smaller. Such fine or ultra-fine particles may be readilyagglomerated in an aqueous medium to form large or agglomeratedparticles in the slurry compositions. In some exemplary embodiments, therare earth element doped in the cerium oxide abrasive particle mayinhibit formation of fine particles or debris, so the amount of largeparticles which may cause scratches on a surface of an object to bepolished may be reduced in the slurry composition.

In some embodiments, the amount of large particles greater than about 2μm dispersed in the slurry composition may be less than about 160 ppm,based on a total weight of the slurry composition. In other exemplaryembodiments, the amount of large particles greater than about 2 μm maybe less than about 110 ppm, less than about 65 ppm, or less than about30 ppm.

The amount of the cerium oxide abrasive particle doped with the rareearth element included in the slurry composition may be changed toimprove dispersibility, the polishing rate, the polishing selectivity,etc. For example, the amount of the abrasive particle may be in a rangeof about 1 to about 10% by weight. In other exemplary embodiments, theamount of the abrasive particle may be from about 2 to about 7% byweight.

The slurry composition may include an aqueous medium for dispersing thecerium oxide abrasive particle doped with the rare earth element. Theaqueous medium may include water and a dispersing agent. The dispersingagent may be a compound capable of dispersing the cerium oxide abrasiveparticle. Non-limiting examples of the dispersing agent may includepoly(acrylic acid), poly(acrylic acid, ammonium salt), poly(acrylicacid, amine salt) and the like.

The amount of the dispersing agent may be changed to improvedispersibility and stability of the slurry composition. For example, theamount of the dispersing agent may be in a range of about 0.05 to about5% by weight. In other embodiments, the amount of the dispersing agentmay be in a range of about 0.1 to about 1% by weight.

In further exemplary embodiments, the slurry composition may optionallyinclude a pH-controlling agent, an additive for improving polishingselectivity, a surfactant or combinations thereof.

In exemplary embodiments, the slurry composition may include apH-controlling agent to improve the polishing rate or polishingselectivity. Examples of an acid pH-controlling agent may include aninorganic acid (e.g., sulfuric acid, hydrochloric acid, nitric acid,phosphoric acid, etc.) and an organic acid (e.g., acetic acid, citricacid, etc.) Examples of a basic pH-controlling agent may include sodiumhydroxide, potassium hydroxide, ammonium hydroxide, quaternary organicammonium hydroxide, etc. The amount of the pH-controlling agent may beproperly changed to consider a final pH.

In some exemplary embodiments, the slurry composition may include anadditive for improving polishing selectivity. When at least twodifferent materials are exposed in a polishing process, the additive mayfunction to selectively remove a specific material relative to othermaterials. For example, the additive disclosed in Korean Patent No.475,457 assigned to Samsung Electronics may be included in the slurrycomposition. The additive disclosed in the patent is a compositionincluding two types of poly(acrylic acid) having differentweight-average molecular weights from each other. The additive may beemployed in selectively polishing silicon oxide relative to siliconnitride. For example, the additive may be used in an amount of about 0.1to about 30% by weight, based on a total weight of the slurrycomposition. The additive may have a pH of about 3 to about 8, or a pHof about 4 to about 7.

In other embodiments, the slurry composition may include a surfactant.Cationic surfactants, anionic surfactants, non-ionic surfactant orcombinations thereof may be used. Examples of the cationic surfactantmay include cetyltrimethyl ammonium bromide, hexadecyltrimethyl ammoniumbromide, cetylpyridinium chloride, etc. Examples of the anionicsurfactant may include sodium dodecyl sulfate, ammonium lauryl sulfate,fatty acid salt, etc. Examples of the non-ionic surfactant may includealkyl poly(ethylene oxide), alkyl poly(propylene oxide), a copolymer ofpoly(ethylene oxide) and poly(propylene oxide), etc. The amount of thesurfactant may be in a range of about 0.001 to about 10% by weight.

Embodiments of the present invention further include methods ofpreparing a slurry composition for CMP. FIG. 3 is a flow chartillustrating a method of preparing a slurry composition according to anexemplary embodiment.

Referring to FIG. 3, a precipitate may be prepared by co-precipitating asalt of a rare earth element and a cerium salt in an aqueous solution(S110).

The salt of a rare earth element and the cerium salt may be dissolved inan aqueous solution (e.g. water) to produce a rare earth metal ion and acerium ion, respectively. Examples of the rare earth element, with theexception of cerium, may include samarium (Sm), scandium (Sc), yttrium(Y), lanthanum (La), praseodymium (Pr), neodymium (Nd), promethium (Pm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium(Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and thelike. These rare earth elements may be used alone or in a combinationthereof. Examples of the rare earth element salt may include a nitrate,a sulfate, a carbonate, a halogenide, a perchlorate, an acetate, anacetyl acetonate, an oxalate or a 2-ethylhexanoate of the rare earthmetal. For example, samarium nitrate, samarium sulfate, samariumcarbonate, samarium acetate, gadolinium nitrate, praseodymium carbonate,etc. may be used. These rare earth element salts may be used alone or ina combination thereof.

Examples of the cerium salt may include cerium nitrate, cerium sulfate,cerium carbonate, cerium halide, cerium perchlorate, cerium acetate,cerium acetyl acetonate, cerium oxalate, cerium 2-ethyl hexanoate, etc.These cerium salts may be used alone or in a combination thereof.

The precipitate obtained by co-precipitation of the rare earth metalsalt and the cerium salt may be homogeneous. For example, theprecipitate may be a nitrate, a carbonate, a sulfate, an acetate, anoxalate or a hydroxide of cerium-rare earth metal. In exemplaryembodiments, a carbonate of cerium-rare earth element may be obtained byco-precipitating an aqueous solution including a cerium salt and a rareearth metal salt with a precipitator (e.g., an inorganic carbonate,urea, etc.). Examples of the precipitator may include ammonium carbonate((NH₄)₂CO₃), ammonium hydrogen carbonate ((NH₄)HCO₃), urea, etc.

The amounts of the cerium salt and the rare earth metal salt may bechanged to control the shape and/or a size of a crystal grain, thepolishing rate, and the amount of large or agglomerated particlesdispersed in an aqueous medium, etc. In some exemplary embodiments, theamount of the rare earth element salt may exceed about 5% by mole, basedon a total mole of the cerium salt and the rare earth element salt. Inother embodiments, the amount of the rare earth element salt may begreater than or equal to about 10% by mole. In still other exemplaryembodiments, the amount of the rare earth element salt may be in a rangeof about 10˜40% by mole, or in a range of about 20˜30% by mole.

The aqueous solution used in preparing the precipitate may includewater, and may optionally include a pH-controlling agent. Examples ofthe pH-controlling agent may include an inorganic acid (e.g., sulfuricacid, hydrochloric acid, nitric acid, etc.), an organic acid (e.g.,acetic acid, citric acid, etc.), or a basic compound (e.g., ammoniumhydroxide, sodium hydroxide, potassium hydroxide, organic ammoniumhydroxide, etc.). The pH of the aqueous solution for precipitation maybe adjusted in a range of about 4 to about 13. The aqueous solution forprecipitation may optionally include a nucleation seed, a dispersingagent, etc.

The precipitate may be prepared by stirring the aqueous solution, inwhich the cerium salt and the rare earth metal salt are dissolved, at atemperature of about 40˜80° C. The reaction time may be properlyadjusted to consider a temperature of the aqueous solution,concentrations of reactants, types of additives, etc.

Referring to FIG. 3, a preliminary cerium oxide abrasive particle dopedwith a rare earth element may be formed by thermally treating theprecipitate (S120). Cerium oxide powder doped with a rare earth elementmay be obtained by thermally treating the precipitate.

The thermal treatment may be performed under an air or oxygen atmosphereto form an oxide. The time of the thermal treatment may be adjusted toconsider the size of grain or particle. For example, the thermaltreatment may be carried out for a period of time in a range from aboutten minutes to about six hours.

The temperature of the thermal treatment may be changed to consider thegrain size, crystal growth rate, etc. For example, the thermal treatmentmay be performed at a temperature of about 500° C. to about 950° C. Inother exemplary embodiments, the thermal treatment may be performed at atemperature of about 600° C. to about 900° C., or about 600° C. to about750° C.

Referring to FIG. 3, a cerium oxide abrasive particle doped with a rareearth element may be formed by grinding the preliminary cerium oxideabrasive particle doped with a rare earth element to control a particlesize and a size distribution (S130). The grinding process may beperformed by a jet milling, a disc milling, a bead milling, etc. Largeor coarse particles may be pulverized while performing the grindingprocess, so a size distribution of the secondary particles may becomesmaller within a specific range. As a result, a cerium oxide abrasiveparticle doped with a rare earth element may be obtained to have auniform size.

In further exemplary embodiments, the cerium oxide abrasive particledoped with the rare earth element may have a mean diameter of a particle(i.e., a secondary particle) in a range of about 50 nm to about 200 nm.In other embodiments, the abrasive particle may have a mean diameter ofabout 70 nm to about 120 nm.

The cerium oxide abrasive particle doped with the rare earth element mayhave an improved fracture strength, as compared with a pure cerium oxideabrasive particle. Pure cerium oxide particles may have a relatively lowfracture strength. Thus, the pure cerium oxide particles may be easy tobreak and a generation of fine or ultra-fine particles or debris muchsmaller than an average-sized particle may increase in the grindingprocess. Such fine or ultra-fine particles may be readily agglomeratedin an aqueous medium to form large or agglomerated particles in theslurry compositions. However, the cerium oxide abrasive particle dopedwith the rare earth element may have a relatively high fracturestrength, so a generation of fine particles or debris may be reduced orsuppressed and the amount of large or agglomerated particles in theslurry composition may be greatly reduced.

Referring to FIG. 3, a slurry composition for CMP may be prepared bydispersing the cerium oxide abrasive particle doped with the rare earthelement in an aqueous medium (S140). The aqueous medium may include adispersing agent and water. The dispersing process may be performedusing a stirrer or a disperser. In some embodiments, the slurrycomposition may optionally include a pH-controlling agent, an additivefor improving polishing selectivity, a surfactant or combinationsthereof.

According to exemplary embodiments, the slurry composition may includethe cerium oxide abrasive particle doped with the rare earth element.The cerium oxide abrasive particle doped with the rare earth element maybe prepared by doping the rare earth element into cerium oxide to have asphere-like shape and a relatively smaller grain size as compared with apure cerium oxide particle. The cerium oxide abrasive particle dopedwith the rare earth element may have an improved fracture strength suchthat generation of fine particles may be suppressed during the grindingprocess and the amount of a large or agglomerated particle dispersed inthe slurry composition may also be reduced. As a result, an abrasiveparticle having a narrow size distribution may be obtained.

Embodiments of the present invention further include methods ofchemically and mechanically polishing an object. FIG. 4 is a flow chartillustrating a method of polishing an object according to exemplaryembodiments. FIG. 5 is a schematic diagram illustrating a CMP apparatusthat may be employed in polishing an object according to furtherexemplary embodiments.

Referring to FIG. 4, a slurry composition including a cerium oxideabrasive particle doped with a rare earth element and an aqueous mediummay be prepared (S210). The slurry composition may be prepared by themethod described with reference to FIG. 3.

Referring to FIGS. 4 and 5, a slurry composition 165 may be providedbetween an object 100 to be polished and a polishing pad 156 (S220). Insome embodiments, a CMP apparatus may include a rotational table 150 onwhich the polishing pad 156 may be located, a rotational axis 153, acarrier 159 for holding the object 100, and a conditioning pad 162 forimproving a surface of the polishing pad 156.

The carrier 159 may be arranged over a portion of the rotational table150, and the conditioning pad 162 may be arranged over a remainingportion of the rotational table 150. The object 100 to be polished maybe mounted on the carrier 159 such that a polishing surface of theobject 100 may face the polishing pad 156 downwards. The object 100located on the carrier 159 may be arranged to make contact with thepolishing pad 156 on the rotational table 150. The carrier 159 holdingthe object 100 may rotate in the same direction as that of therotational axis 153. Rotational speeds of the carrier 159 and therotational axis 153 may be different from each other.

The slurry composition 165 may be provided from a providing nozzle (notillustrated) located over the rotational table 150 toward a centerportion of the polishing pad 156. The slurry composition 165 dropped onthe polishing pad 156 may move toward an edge portion of the polishingpad 156 due to the centrifugal force. Accordingly, the slurrycomposition 165 may be provided between the polishing pad 156 and theobject 100.

The object 100 may be a semiconductor substrate, or a semiconductorsubstrate on which various structures (e.g., a layer, a film, a wiring,a pad, a plug, a gate, a capacitor, etc.) may be formed. In exemplaryembodiments, the object 100 may be a substrate on which an insulationlayer (e.g., an oxide layer, a nitride layer, an oxynitride layer, alow-dielectric (k) layer or a high-k layer) may be formed. In otherembodiments, the object 100 may be a substrate on which a metal layer(e.g., a tungsten layer, a copper layer, an aluminum layer, etc.) may beformed.

In further exemplary embodiments, the object 100 may be a substrate onwhich an insulation layer for forming an isolation layer may be formed.For example, the insulation layer for forming an isolation layer may beformed on a substrate to fill a trench formed at the substrate. Theinsulation layer may be formed using silicon oxide, silicon oxynitride,silicon nitride, etc.

In some embodiments, the object 100 may be a substrate on which aninsulating interlayer may be formed. For example, the insulatinginterlayer may be formed on the substrate having a conductive structure(e.g., a conductive line, a conductive pad, etc.) to cover theconductive structure. The insulating interlayer may be formed usingsilicon oxide, silicon oxynitride, silicon nitride, etc.

The surface of the object 100 may be polished by contacting the object100 with the polishing pad 156 (S230). Contacting the object 100 withthe polishing pad 156 may be performed while a down pressure (I) isapplied to the object from the carrier 159 and rotations (II, III) ofthe polishing pad 156 and the carrier 159 is adjusted. The surface ofthe object 100 may be mechanically rubbed by the abrasive particle andprotrusions of the polishing pad 156. Simultaneously, the surface of theobject 100 may be reacted with chemical components of the slurrycomposition to remove or etch the object 100.

According to exemplary embodiments, the slurry composition 165 includesthe cerium oxide abrasive particle doped with the rare earth element andthe aqueous medium. The cerium oxide abrasive particle doped with therare earth element may have proper shape and/or size for reducing ageneration of a scratch defect on a surface of an object as comparedwith a pure cerium oxide abrasive particle. The cerium oxide abrasiveparticle doped with the rare earth element may also have an improvedfracture strength so that generation of debris or fine particles may bereduced during a grinding process and the amount of a large oragglomerated particle dispersed in the slurry composition may also bereduced. The slurry composition 165 may reduce generation of a defect(e.g., a scratch) on the object 100 by employing such an abrasiveparticle having a controlled shape and size of a crystal grain and anarrow distribution of a particle diameter.

Embodiments of the present invention include methods of manufacturing asemiconductor device. FIGS. 6A to 6D are cross-sectional viewsillustrating a method of manufacturing a semiconductor device accordingto some exemplary embodiments.

Referring to FIG. 6A, a pad oxide layer 205 and a pad nitride layer 210may be sequentially formed on a substrate 200. For example, thesubstrate 200 may be a semiconductor substrate such as a silicon wafer,a silicon-germanium substrate, an SOI substrate, etc. The pad oxidelayer 205 may be formed on the substrate 200 to reduce a stress betweenthe substrate 200 and the pad nitride layer 210. In some embodiments,the pad oxide layer 205 may be formed by performing a thermal oxidationor a chemical vapor deposition (CVD).

The pad nitride layer 210 may be formed on the substrate 200 on whichthe pad oxide layer 210 is formed. The pad nitride layer 210 may be usedas a mask for forming a trench 220 (see FIG. 6B) in the substrate 200.In some embodiments, the pad nitride layer 210 may be formed byperforming a low pressure CVD or a plasma-enhanced CVD using an SiH₂Cl₂gas, an SiH₄ gas, an NH₃ gas, etc.

A photoresist pattern 215 may be formed on the pad nitride layer 210.The photoresist pattern 215 may be used as a mask for patterning the padnitride layer 210 and the pad oxide layer 205. In exemplary embodiments,the photoresist pattern 215 may be formed by coating the pad nitridelayer 210 with a photoresist composition and by performing an exposureprocess and a developing process on a photoresist film.

Referring to FIG. 6B, the pad nitride layer 210 and the pad oxide layer205 may be partially etched using the photoresist pattern 215 as anetching mask to form a pad nitride layer pattern 210 a and the pad oxidelayer pattern 205 a. The pad nitride layer pattern 210 a and the padoxide layer pattern 205 a may be a mask pattern for forming the trench220 in the substrate 200. In exemplary embodiments, the photoresistpattern 215 may be removed from the substrate 200 by an ashing processand/or a stripping process after forming the pad nitride layer pattern210 a and the pad oxide layer pattern 205 a on the substrate 200.

The trench 220 may be formed by etching a portion of the substrate 200exposed by the pad nitride layer pattern 210 a and the pad oxide layerpattern 205 a. The trench may define an active region and a fieldregion. The trench 220 may have an inclined sidewall relative to avertical direction of the substrate 200. For example, the trench 220 maybe formed by an anisotropic etching process.

In exemplary embodiments, a liner layer (not illustrated) may beoptionally formed on a bottom and a sidewall of the trench 220. Theliner layer may be formed to cure damage generated on an exposed surfaceof the substrate 200 and to suppress occurrence of a leakage current.For example, the liner layer may be formed by thermally oxidizing thesurface of the substrate 200 exposed by the trench 220, or by deposingan insulation material (e.g., silicon nitride).

Referring to FIG. 6C, an insulation layer 225 may be formed on thesubstrate 220 using an insulation material. The insulation layer 225 maybe formed on the pad nitride layer 210 a to fill the trench 220.

In some embodiments, the insulation layer 225 may be formed by a siliconoxide. Examples of silicon oxides may include tetraethyl orthosilicate(TEOS), plasma-enhanced TEOS (PE-TEOS), O₃-TEOS, borophosphosilicateglass (BPSG), phosphosilicate glass (PSG), undoped silicate glass (USG),spin-on glass (SOG), high density plasma CVD oxide, and the like.

Referring to FIG. 6D, a polishing process may be performed using aslurry composition for CMP on the substrate 200 on which the insulationlayer 225 may be formed. The polishing process may be performed until anupper face of the pad nitride layer pattern 225 is exposed to form aninsulation layer pattern 225 a in the trench 220.

During the polishing process, the slurry composition according toexemplary embodiments may be applied. The slurry composition may includea cerium oxide abrasive particle doped with a rare earth element and anaqueous medium. The cerium oxide abrasive particle doped with the rareearth element may have a proper shape and/or size for reducinggeneration of a scratch defect on a surface of an object as comparedwith a pure cerium oxide abrasive particle. The cerium oxide abrasiveparticle doped with the rare earth element may also have an improvedfracture strength so that generation of debris or fine particles may bereduced during a grinding process and an amount of a large oragglomerated particle dispersed in the slurry composition may also bereduced. The slurry composition may reduce generation of a defect (e.g.,a scratch) on the insulation layer pattern 225 a by employing such anabrasive particle having a controlled shape and size of a crystal grainand a narrow distribution of a particle diameter.

When the insulation layer 225 is formed using silicon oxide, the padnitride layer pattern 210 a may be provided as a polishing stop layer.In this case, the slurry composition may include an additive forimproving polishing selectivity. The additive disclosed in Korean PatentNo. 475,457 may be added to the slurry composition.

The insulation layer pattern 225 may be formed by a polishing processusing the cerium oxide abrasive particle doped with a rare earth elementto reduce defects of a device. Although not illustrated in the drawings,the pad nitride layer pattern 210 a and the pad oxide layer pattern 205a may be sequentially removed from the substrate 200 after forming theinsulation layer pattern 225 in the trench 220. A tunnel oxide layer, afloating gate, a dielectric layer and a control gate may be sequentiallyformed on exposed portions of the substrate 200. Accordingly, anon-volatile memory device (e.g., a flash memory) may be manufactured onthe substrate 200.

FIGS. 7A to 7C are cross-sectional views illustrating a method ofmanufacturing a semiconductor device according to other exemplaryembodiments.

Referring to FIG. 7A, a conductive structure 315 may be formed on asubstrate 300 to have a conductive layer pattern 305 and a mask layerpattern 310. The conductive structure 315 may be a conductive line, awiring, a gate, etc. For example, the substrate 200 may be asemiconductor substrate such as a silicon wafer, a silicon-germaniumsubstrate, an SOI substrate, etc. The substrate 300 may include otherlower structures (not illustrated). The lower structures may include acontact region, a pad, a plug, a conductive wiring, a conductivepattern, an insulation layer, etc.

In some embodiments, the conductive layer pattern 305 may be formed onthe substrate 300 to be electrically connected to the lower structurehaving conductivity. In other embodiments, an insulation layer may beoptionally formed between the conductive layer pattern 305 and thesubstrate 300. The insulation layer may be provided as a gate insulationlayer, a tunnel oxide layer, etc.

In exemplary embodiments, a conductive layer and a mask layer may besequentially formed on the substrate 300. A photoresist pattern (notillustrated) may be formed on the mask layer, and then the conductivelayer and the mask layer may be sequentially patterned using thephotoresist pattern as an etching mask to form the conductive layerpattern 305 and the mask layer pattern 310.

The conductive layer may be formed using, for example, dopedpolysilicon, tungsten (W), aluminum (Al), copper (Cu), titanium (Ti),tungsten nitride (WNx), aluminum nitride (AlNx), titanium nitride(TiNx), titanium aluminum nitride (TiAlxNy) and the like. The conductivelayer may be formed by a sputtering, CVD, an atomic layer deposition(ALD) or a pulse laser deposition process. The mask layer may be formedusing, for example, silicon nitride, silicon oxynitride, metal nitride,etc.

Referring to FIG. 7B, a preliminary insulating interlayer 320 may beformed on the substrate 300 on which the conductive structure 315 may beformed. The preliminary insulating interlayer 320 may be formed to coverthe conductive structure 315. In example embodiments, the preliminaryinsulating interlayer 320 may be formed using a silicon oxide. Examplesof silicon oxide may include TEOS, PE-TEOS, O₃-TEOS, BPSG, PSG, USG,SOG, HDP-CVD oxide, etc. For example, the preliminary insulatinginterlayer 320 may be formed by a CVD, a PE-CVD, an ALD or a HDP-CVD.

Referring to FIG. 7C, a polishing process may be performed on thepreliminary insulating interlayer 320 using a slurry composition for CMPto form an insulating interlayer 320 a. In exemplary embodiments, thepolishing process may be performed until an upper face of the conductivestructure 315 is exposed. In this case, the mask layer pattern 310 mayact as a polishing stop layer. In other embodiments, the polishingprocess may be performed such that the conductive structure may not beexposed.

The polishing process may be performed using the slurry compositionaccording to exemplary embodiments. The slurry composition may include acerium oxide abrasive particle doped with a rare earth element and anaqueous medium. The slurry composition may reduce generation of a defect(e.g., a scratch) on the insulating interlayer 320 a by employing suchan abrasive particle having a controlled shape and size of a crystalgrain and a narrow distribution of a particle diameter.

Exemplary embodiments of the present invention will be further describedhereinafter with reference to Synthetic Examples, Examples andComparative Examples regarding preparation of slurry compositions. Theseexamples are illustrative of embodiments of the present invention andare not intended to be limiting of the present invention.

Preparation of a Cerium Oxide Abrasive Particle Doped with a Rare EarthElement

Synthetic Example 1

A cerium oxide abrasive particle doped with samarium (Sm) was prepared.A homogeneous precipitate of samarium-cerium carbonate(Ce_(x)Sm_(y)(CO₃)₃) was prepared by co-precipitating cerium nitrate(Ce(NO₃)₃.6H₂O) and samarium nitrate (Sm(NO₃).2H₂O) in an aqueoussolution. After dissolving polyethylene glycol having a weight-averagemolecular weight of about 600 in water, cerium nitrate and samariumnitrate were dissolved in the aqueous solution with a molar ratio ofabout 70% (Ce) and about 30% (Sm). A nucleation seed was also added tothe aqueous solution. An excess amount of ammonium hydrogen carbonate(NH₄HCO₃) as a precipitator was added to the aqueous solution, and thenthe mixture was stirred at a temperature of about 70° C. with a speed ofabout 80 rpm until the amount of a precipitate did not further increase.The stirring time for precipitation was about 12 hours, and then themixture was stabilized for an additional 12 hours. The reaction wascarried out under a pH of about 5.5.

The samarium cerium carbonate precipitate was thermally treated at atemperature of about 650° C. to form a powder of samarium cerium oxide.The thermal treatment was performed under air for about 6 hours. Thesamarium cerium oxide powder was grinded by milling to form a ceriumoxide abrasive particle doped with samarium having a controlled sizedistribution. The grinding was performed using a horizontal millingmachine and a zirconium bead such that the Sm-doped cerium oxideabrasive particle had a mean diameter of about 120 nm.

A grain shape of the obtained Sm-doped cerium oxide abrasive particlewas determined by observing the particle using an electron microscope. Amean diameter of the crystal grain (i.e., a primary particle) of theobtained Sm-doped cerium oxide abrasive particle was determined by anX-ray diffraction analysis and Scherrer's equation. The analysis resultsare shown in Table 1 below.

Synthetic Examples 2 through 5 and Comparative Synthetic Example 1

Abrasive particles were prepared by the method substantially the same asthe method of Synthetic Example 1 except that the amount of samariumnitrate and cerium nitrate were changed. Shapes and sizes of crystalgrains were analyzed, and the results are shown in Table 1.

Synthetic Example 6

Sm-doped cerium oxide abrasive particles were prepared by the methodsubstantially the same as the method of Synthetic Example 1 except thatsamarium nitrate and cerium nitrate were used with a molar ratio ofabout 25% (Sm) and about 75% (Ce), and the grinding process wasperformed such that a mean diameter of the abrasive particle was about105 nm.

TABLE 1 Sm Ce Grain Size [mol %] [mol %] [nm] Grain Shape SyntheticExample 1 30 70 26.5 spherical Synthetic Examples 2, 6 25 75 27spherical Synthetic Example 3 20 80 27 spherical Synthetic Example 4 1090 27 semi-spherical Synthetic Example 5 5 95 29 faceted ComparativeSynthetic 0 100 32 faceted Example 1

As shown in Table 1, it was observed that the pure cerium oxide particleprepared in Comparative Synthetic Example 1 had a faceted crystal grain.However, it was confirmed that cerium oxide particles doped withsamarium of at least 10 mol % had a spherical or semispherical crystalgrain. Additionally, the pure cerium oxide particle prepared inComparative Synthetic Example 1 had a grain size of about 32 nm.Sm-doped cerium oxide particles prepared in Synthetic Examples 1˜4 had agrain size of 27 nm or less, as being smaller than the grain size of thepure cerium oxide particle. Accordingly, it may be noted that doping ofthe rare earth element may form a sphere-like grain and reduce the sizeof a crystal grain.

Such a sphere-like shape and a size decrease of a crystal grain may becaused by crystal growth inhibition of the rare earth element acting asa solid solute. The rare earth element may prevent cerium oxide fromgrowing into a cubic shape. As shown in FIG. 1, pure or undoped ceriumoxide may have a tendency to grow with a faceted shape to have a crystalface. As shown in FIG. 2, however, the rare earth element may cause auniform growth of crystal faces [111] and [100] in cerium oxide, andthus, a sphere-like crystal grain may be obtained.

Preparation of Slurry Compositions for Chemical Mechanical PolishingExample 1

A slurry composition was prepared using the Sm-doped cerium oxideabrasive particles prepared in Synthetic Example 6. The abrasivecomposition was obtained by dispersing the Sm-doped cerium abrasiveparticles in an aqueous medium including water and poly(acrylic acid).About 5% by weight of the abrasive particle, about 1% by weight ofpoly(acrylic acid) and about 94% by weight of water were used, based ona total weight of the abrasive composition. The additive compositiondisclosed in Korean Patent No. 475,457 assigned to Samsung Electronicswas prepared to improve a polishing selectivity. The additivecomposition having a pH of about 6.5 was prepared. The abrasivecomposition, the additive composition for improving a polishingselectivity and water were mixed together with a volume ratio of about1:3:3. A slurry composition was prepared by filtrating the mixture usinga 10 μm filter supplied by Pall Corp.

Comparative Example 1

A slurry composition was prepared by the method substantially the sameas the method of Example 1 except that a commercial abrasive compositionincluding pure cerium oxide abrasive particles was used instead theabrasive composition. A commercial cerium oxide abrasive composition(HS8005-A) provided by Hitach in Japan was used as a pure cerium oxideabrasive composition.

Example 2

A slurry composition was prepared using the Sm-doped ceria abrasiveparticle prepared in Synthetic Example 1. About 5% by weight of theabrasive particle, about 1% by weight of poly(acrylic acid) and about94% by weight of water were used, based on a total weight of the slurrycomposition, and then the mixture was filtrated by a 10 μm filtersupplied by Pall Corp.

Examples 3 through 6 and Comparative Example 2

Slurry compositions were prepared by the method substantially the sameas the method of Example 2 except that the abrasive particles preparedin Synthetic Examples 2-5 and Comparative Synthetic Example 1 were usedas abrasive particles.

Evaluation of a Distribution of a Particle Diameter

Sizes of the primary particle (i.e., grain) and a secondary particle,size distributions and amounts of large agglomerated particles dispersedin the slurry compositions were analyzed. The particle size was measuredusing an electron microscope, and the amount of large particles largerthan about 2 μm were measured by a quantitative filtration method (QFM).The results are shown in Table 2 below and FIGS. 8 through 10.

TABLE 2 Example 1 Comparative Example 1 Abrasive Particle Sm-dopedCommercial Undoped Ceria Ceria Primary Particle (grain) [nm] 27 30.5Secondary Particle [nm] 105 124 Large Particle [>2 μm, ppm] 15 103

Referring to Table 2, it was observed that the commercial undoped ceriumoxide abrasive had a grain size of about 30.5 nm and a secondaryparticle diameter of about 124 nm, and produced large particles greaterthan about 2 μm in the slurry composition with an amount of about 103ppm. However, it was observed that the Sm-doped cerium oxide abrasivehad a grain size of about 27 nm and a secondary particle diameter ofabout 105 nm, and produced large particles greater than about 2 μm inthe slurry composition with an amount of about 15 ppm. Accordingly, itmay be noted that the Sm-doped cerium oxide abrasive particle may haveprimary and secondary particles that are smaller than those of undopedcerium oxide abrasive particles, and Sm-doped cerium oxide abrasiveparticles may greatly reduce the amount of large particles greater thanabout 2 μm in the slurry composition.

FIG. 8 is a graph showing size distributions of abrasive particlescontained in the slurry compositions obtained in Example 1 andComparative Example 1. FIGS. 9 and 10 are electron microscopic picturesshowing abrasive particles included in the slurry compositions obtainedin Example 1 and Comparative Example 1, respectively.

Referring to FIGS. 8 through 10, it may be noted that the Sm-dopedcerium oxide abrasive particles dispersed in the slurry composition ofExample 1 may have a size distribution much narrower than that ofundoped cerium oxide abrasive particles dispersed in the slurrycomposition of Comparative Example 1. It may also be noted that theslurry composition including the Sm-doped cerium oxide abrasiveparticles may have the reduced amounts of fine particles smaller than amean particle size and large particles greater than about a meanparticle size. These results may be caused by a relatively strongfracture strength and/or a sphere-like grain shape of Sm-doped ceriumoxide abrasive particles such that a generation of fine particles ordebris may be suppressed during a grinding process. At least due to thestrong fracture strength, the particles may be broken along the crystalshape, and a highly uniform abrasive particle may be obtained.

Evaluation of Polishing Characteristics of Slurry Compositions

Polishing characteristics of the slurry compositions prepared in Example1 and Comparative Example 1 were evaluated. A polishing rate of asilicon oxide layer and the number of scratches were measured. Thesilicon oxide layer was prepared by depositing PE-TEOS on a bare siliconwafer with a thickness of about 12,000 Å. Mirra (manufactured by AMAT inU.S.A.) was used as a polishing apparatus. A down pressure of apolishing pad was about 3.0 psi, a rotational speed of a table was about108 rpm, a rotational speed of a head holding the silicon wafer wasabout 102 rpm, a polishing time was about 60 seconds, and a flow rate ofthe slurry composition was about 150 mL per minute.

After performing the polishing process, the silicon wafer was cleanedusing a hydrogen fluoride (HF) aqueous solution diluted with a volumeratio of 100:1 (DIW:HF). The number of scratches was analyzed using adefect detector (AIT-UV). The total number of scratches and the numberof deep scratches were measured. The results relating to the polishingrate are shown in Table 3 below, and the results relating to the numberof scratches are shown in Table 4 below.

TABLE 3 Polishing rate of Error range oxide layer [Å/min] [Å/min]Example 1 2,480 105 Comparative Example 1 2,600 125

TABLE 4 Total number of Number of scratches deep scratches Example 1 2503 Comparative Example 1 700 18

Referring to Tables 3 and 4, the slurry composition including theSm-doped cerium oxide abrasive particles prepared in Example 1 showed aslightly reduced polishing rate of the silicon oxide layer, as comparedwith the slurry composition including undoped cerium oxide abrasiveparticles prepared in Comparative Example 1. It may be noted that thereis not a significant difference in the polishing efficiency.

The slurry composition including the Sm-doped cerium oxide abrasiveparticle prepared in Example 1 may greatly reduce scratch defects. Theslurry composition including undoped cerium oxide abrasive particlesprepared in Comparative Example 1 generated about 700 scratches in totaland about 18 deep scratches, whereas the slurry composition includingthe Sm-doped cerium oxide abrasive particles prepared in Example 1generated about 250 scratches in total and about 3 deep scratches. Itmay be noted that the composition of Example 1 may reduce the totalnumber of scratches by about 64%, and the number of deep scratches byabout 83%, as compared with the composition of Comparative Example 1.Accordingly, it may be noted that doping a cerium oxide abrasiveparticle with a rare earth element may greatly reduce the number ofscratches on a surface of an object to be polished.

Additionally, a polishing process for forming an isolation layer in atrench was performed using the slurry compositions prepared in Example 1and Comparative Example 1. A trench was formed in a silicon wafer, andthen a silicon oxide layer on the silicon wafer to fill the trench. Thesilicon oxide layer was formed using PE-TEOS. A CMP process wasperformed on the silicon oxide layer to form an isolation layer in thetrench. A width of the trench was about 70 nm. The polishing process wasperformed under conditions substantially the same as those in thepolishing process relating to Table 3 and 4. After performing thepolishing process, the number of scratches was measured using a defectdetector (AIT-UV). The total number of scratches and the number of deepscratches were measured. The results relating to the number of scratchesare shown in Table 5 below and FIGS. 11 and 12. FIGS. 11 and 12 arewafer maps illustrating a distribution of scratch defects on a waferpolished using each of the slurry compositions obtained in Example 1 andComparative Example 1.

TABLE 5 Total number of Number of scratches deep scratches Example 1 9 3Comparative Example 1 19 16

Referring to Table 5 and FIGS. 11 and 12, the slurry compositionincluding the Sm-doped cerium oxide abrasive particles prepared inExample 1 may reduce scratch defects on a surface of the isolationlayer, as compared with undoped cerium oxide abrasive particles.Particularly, the slurry composition including the Sm-doped cerium oxideabrasive particles prepared in Example 1 may greatly reduce deepscratches on the isolation, since the Sm-doped cerium oxide abrasiveparticles have a sphere-like grain shape and a substantially reducedamount of large particles.

Evaluations of Amounts of Large Particles and the Number of ScratchesAccording to Doping Amount of a Rare Earth Element

The amounts of large particles dispersed in the slurry compositionsprepared in Examples 2 through 6 and Comparative Example 2 weremeasured, and the number of scratches was also measured. The amount oflarge particles larger than about 2 μm was measured by a quantitativefiltration method (QFM). The polishing process was performed on asilicon oxide layer, which was prepared by depositing PE-TEOS on a baresilicon wafer with a thickness of about 12,000 Å. Mirra (manufactured byAMAT in U.S.A.) was used as a polishing apparatus. A down pressure of apolishing pad was about 3.0 psi, a rotational speed of a table was about108 rpm, a rotational speed of a head holding the silicon wafer wasabout 102 rpm, a polishing time was about 60 seconds, and a flow rate ofthe slurry composition was about 150 mL per minute. After performing thepolishing process, the silicon wafer was cleaned using an HF aqueoussolution diluted with a volume ratio of 100:1 (DIW:HF). The number ofscratches was analyzed using a defect detector (AIT-UV). The totalnumber of scratches and the number of deep scratches were measured. Therelative ratio of scratches was evaluated, based on the number 100% ofscratches generated using the slurry composition prepared in ComparativeExample 2. The results are shown in Table 6 below and FIG. 13. FIG. 13is a graph showing the number of scratches generated on a waferaccording to the doping amount of the rare earth element.

TABLE 6 Abrasive Particles Large Scratches Sm Mean Particles Relative[mol Ce Diameter [>2 μm, Ratio %] [mol %] [nm] ppm] Number [%] Example 230 70 120 54 8 25 Example 3 25 75 120 65 8 25 Example 4 20 80 120 103 1237 Example 5 10 90 120 158 15 47 Example 6 5 95 120 182 24 75Comparative 0 100 120 210 32 100 Example 2

Referring to Table 6 and FIG. 13, it can be noted that the slurrycomposition including the Sm-doped cerium oxide abrasive particle has arelatively small amount of large particles, as compared with the slurrycomposition including the undoped cerium oxide abrasive particle. Thecomposition of Comparative Example 2 included about 210 ppm of largeparticles greater than about 2 μm, whereas the composition of Examples 2through 6 included at most about 182 ppm of large particles greater thanabout 2 μm. When the amount of samarium is greater than or equal toabout 10% by mole, the amount of large particles greater than about 2 μmwas about 158 ppm or less. Such an amount of large particles may reflecta decrease of at least about 25%, based on the amount of large particlesin the case of using the undoped cerium oxide abrasive particles.

Further, doping the cerium oxide abrasive particles with the rare earthelement may greatly reduce the number of scratches. When the amount ofsamarium is greater than or equal to about 10% by mole, the number ofscratches generated on a surface of the polished object may be reducedwith at least about 50%.

According to exemplary embodiments, the slurry composition includes acerium oxide abrasive particle doped with a rare earth element. Thecerium oxide abrasive particle doped with a rare earth element may haveproper shape and/or size for reducing generation of a scratch defect ona surface of an object as compared with a pure cerium oxide abrasiveparticle. The cerium oxide abrasive particle doped with a rare earthelement may have an improved fracture strength so that generation ofdebris or fine particles may be reduced during a grinding process andthe amount of a large or agglomerated particle dispersed in the slurrycomposition may also be reduced. The slurry composition may reducegeneration of a defect (e.g., a scratch) on an object by employing suchan abrasive particle having a controlled shape and size of a crystalgrain and a narrow distribution of a particle diameter.

The foregoing is illustrative of exemplary embodiments and is not to beconstrued as limiting thereof. Although a few exemplary embodiments havebeen described, those skilled in the art will readily appreciate thatmany modifications are possible in the exemplary embodiments withoutmaterially departing from the novel teachings of the embodiments.Accordingly, all such modifications are intended to be included withinthe scope of the present invention as defined in the claims. In theclaims, means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures. Therefore, it maybe to be understood that the foregoing may be illustrative of variousexample embodiments and is not to be construed as limited to thespecific example embodiments disclosed, and that modifications to thedisclosed example embodiments, as well as other example embodiments, areintended to be included within the scope of the appended claims.

1-14. (canceled)
 15. A method of chemically and mechanically polishingan object, comprising: providing a slurry composition between an objectand a polishing pad, the slurry composition including a cerium oxideabrasive particle having a rare earth element as a dopant, and anaqueous medium for dispersing the cerium oxide abrasive particle, withthe proviso that the rare earth element is not cerium; and polishing asurface of the object by contacting the object with the polishing pad.16. The method of claim 15, wherein the object comprises: a substratehaving a trench; and an insulation layer on the substrate to fill thetrench.
 17. The method of claim 16, wherein polishing the surface of theobject comprises polishing the insulation layer until an upper face ofthe substrate is exposed to form an isolation layer in the trench. 18.The method of claim 15, wherein the object comprises: a substrate onwhich a conductive structure is formed; and an insulating interlayer onthe substrate to cover the conductive structure.
 19. The method of claim1, wherein the rare earth element comprises samarium (Sm).
 20. Themethod of claim 1, wherein an amount of the rare earth element is in arange of about 10 to about 40% by mole, based on a total mole of ceriumand the rare earth element.
 21. The method of claim 20, wherein theamount of the rare earth element is in a range of about 20 to about 30%by mole, based on a total mole of cerium and the rare earth element. 22.The method of claim 1, wherein the cerium oxide abrasive particle has amean grain diameter of less than about 29 nm.
 23. The method of claim 1,wherein the ceria abrasive particle has a mean diameter of a secondaryparticle in a range of about 70 nm to about 120 nm.
 24. The method ofclaim 1, wherein the cerium oxide abrasive particle doped with the rareearth element has a sphere-like grain.
 25. The method of claim 1,wherein the aqueous medium comprises a dispersing agent and water, andan amount of the dispersing agent is in a range of about 0.05 to about5% by weight, based on a total weight of the slurry composition.
 26. Themethod of claim 1, wherein an amount of the cerium oxide abrasiveparticle is in a range of about 1 to about 10% by weight, based on atotal weight of the slurry composition.
 27. The method of claim 1,wherein the cerium oxide abrasive particle is prepared by performing athermal treatment on a precipitate obtained by co-precipitating a ceriumsalt and a salt of a rare earth element in an aqueous solution, and bygrinding the thermally treated precipitate, with the proviso that therare earth element is not cerium.